The present invention relates to room-temperature curable coatings and more particularly to such a coating which has been adapted for application to the interior or exterior of pipe.
Cast iron or other metal pipe is lined or coated conventionally for conveying sewage, water, or other material. Such pipe lining is needed in order to protect the pipe against corrosion from moderately acidic or basic sewage or from oxidation by potable or ground water. Accordingly, a suitable pipe lining must possess several unique characteristics in order to find success in the marketplace. Such characteristics include: (1) the cured film must not crack or separate from the pipe when subjected to a 15% ring deflection (i.e. deflection of pipe by 15% of its cross-sectional diameter); (2) the coating composition may not contain any acid radicals or chloride groups; (3) the coating must be UV resistant; (4) the coating composition must be compatible with neutral inorganic fillers; (5) the cured film must be tough, flexible, and non-porous; (6) the coating composition should cure within three minutes maximum and preferably within one minute; (7) the coating composition should be composed of no more than two liquid components; (8) the cured film must be resistant to moderate acidity or basicity; and ( 9) the cured film must withstand temperatures ranging from about -20.degree. to about 80.degree. C.
Heretofore, cement has been used as a pipe lining, but cement often is slow curing, inflexible, porous, and prone to degradation in acidic and basic environments. Coal tar epoxies or polyethylene beads also have been used, but such materials are thermoplastic and require the pipe to be heated to about 370.degree. C. to melt these materials and cause them to flow and evenly coat the pipe. Such heating step is energy intensive and less productive due to the relatively long heating and cooling cycles required.